Use proper descriptors array when committing state to JSON object.

src/json-parser.cc

Index: src/json-parser.cc
diff --git a/src/json-parser.cc b/src/json-parser.cc
index 50c51b0ac5293969539a0735c700c34903cc413b..7c0a83c5d9d7016b8afc93b10b7b41b444278b84 100644
--- a/src/json-parser.cc
+++ b/src/json-parser.cc
@@ -478,7 +478,7 @@ void JsonParser<seq_one_byte>::CommitStateToJsonObject(
   DCHECK(!json_object->map()->is_dictionary_map());
 
   DisallowHeapAllocation no_gc;
-  DescriptorArray* descriptors = map->instance_descriptors();
+  DescriptorArray* descriptors = json_object->map()->instance_descriptors();
   int length = properties->length();
   for (int i = 0; i < length; i++) {
     Handle<Object> value = (*properties)[i];